Several regimes of pamaquin (plasmochin) were given a therapeutic trial in mosquito-induced vivax malaria (Chesson strain).
The administration of daily doses of 63 milligrams of the base or 140 milligrams of the naphthoate salt, or less, concurrently with quinine for 14 days protected only a few of the subjects against relapse. No protection was afforded when the drugs were given serially. The effect was not appreciably enhanced when pamaquin (31 milligrams of the base a day) was administered concurrently with several other experimental drugs.
The average percentage of total hemoglobin converted to methemoglobin was a useful measure for the comparison of the toxicity of various regimes of pamaquin.
Standardized clinical trials diminished the influence of variables, such as acquired and natural immunity, variations in intensity of infection, the effect of suppressive drugs, and strain differences, which confuse the interpretation of results in field studies.